The present invention concerns a radially undulating shaft seal having a seal axis and a lip of polymeric material that surrounds the shaft to be sealed, wherein the lip is demarcated on the inside by an inner surface that tapers out in the form of a hollow cone toward the side facing away from the space being sealed and wherein the lip has ribs that project radially inward, distributed uniformly around it.
A radially undulating shaft seal of this type is known from the German Pat. No. 1 153 578. It has undulating ribs on the face of its lip that, in conjunction with a lip-traveling surface that has ribs that extend at an angle to the axis of the seal, pump the medium being sealed toward the space being sealed. The operational life of such a radially undulating shaft seal is not entirely satisfactory. When the lip on the seal is inadequately lubricated, it is subjected to excessive wear by the rotating shaft. As time passes the seal will accordingly become less effective, especially at times when the shaft is not moving.